Integrated circuits often include internal voltage generation circuitry to provide internal voltages. In a DRAM memory device, for example, a word line precharge voltage is used during memory access operations. This voltage is often generated using an internal voltage generator circuit. In addition, a substrate voltage, VBB, can be provided by a voltage pump circuit to generate a substrate bias negative voltage.
In a DRAM device, VBB pumps are traditionally turned off during a memory cell self-refresh operation, or device power-down since there is no current demand for VBB. However, in some new memory devices a word line voltage generator provides a negative voltage (for example about −0.3 V) using the VBB pump. As such, VBB current is consumed during a memory cell self-refresh operation. As shown in FIG. 1 a prior art word line voltage generator includes an inverting amplifier 100 to generate a word line reference voltage (Vnwl) of about −0.3 V. Several unit gain power amplifier stages 110 are provided for different circuits distributed in the memory device. In a self-refresh operation or power down condition, the inverting amplifier and at least one unit gain amplifier are enabled. These two amplifiers can consume an undesired amount of current.
What is needed is an improved voltage generator circuit that can provide a negative voltage from VBB for using in integrated circuits, such as memory devices.